One estimate of weld strength is the diameter of the nugget formed by the weld. Prior art attempts to estimate the diameter of a nugget created by a weld have focused on certain weld parameters, such as, current, voltage, applied force, and weld time. Other attempts have attempted to measure resistance across a weld nugget. Other attempts require the utilization and destruction of many workpieces, requiring significant material and labor expense. Continuous online estimation of dynamic resistance has been considered difficult due to inductive noise. Furthermore, the nugget diameter will vary depending on the type of controller, and type of welding strategy used.
It is therefore desirable to provide a method of estimating weld nugget diameter that overcomes these disadvantages.